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1、Three-phase bridge inverterSynthesis of voltage waves in bridge inverter(a)Output phase voltage and current waves assuming perfect filter (b)input dc current wavePrinciple of dual bridge 12-step inverter(bypass diodes omitted)串联单相三重逆变器串联单相三重逆变器串联三相二重串联三相二重12脉冲逆变器脉冲逆变器串联三相三重串联三相三重18脉冲逆变器脉冲逆变器并联三相多重逆变
2、器并联三相多重逆变器（中心抽头电抗器方式）（中心抽头电抗器方式）并联三相多重逆变器（并联多重变压器方式）Principle of sinusoidal pulse width modulation(generation of control signals)Principle of sinusoidal pulse width modulation(modulated waveform for p=6)Sinusoidal pulse width modulationVaVTVbHarmonic content of the sinusoidal PWM voltage as a functi
3、on of modulation index(a)harmonic amplitude relative to maximum fundamental amplitudeHarmonic content of the sinusoidal PWM voltage as a function of modulation index(b)harmonic amplitude relative to actual fundamental amplitudeRelation of fundamental frequency with carrier frequency of transistor in
4、verterPulse width modulation with uniform samplingHarmonic elimination method(1)Voltage wave in harmonic elimination methodHarmonic elimination method(2)Harmonic elimination method(3)Harmonic elimination method(4)Harmonic elimination method(5)Notch angle relation with fundamental output voltage for
5、5th and 7th harmonic eliminationPWM for minimum loss in motorDynamic braking(1)能量只在一个方向流动的变频系统Dynamic braking(2)Dynamic braking capacity(a)PWM and(b)square-wave inverterDual GTO PWM inverter for bidirectional power flowThe three-phase bridge autosequentially commutated current-source inverter with a
6、 wye-connected RL road(a)Circuit diagram;(b)(c)(d)idealized ac line current waveforms;(e)Thyristor gating sequenceIdealized voltage and current waveforms for an induction motor fed by a six-step current source inverter(a)approximate induction motor equivalent circuit;(b)(c)(d)voltage and current wav
7、eformsPWM current source inverter(1)PWM current source inverter(2)电压源型与电流源型变频器主要特点比较电压源型与电流源型变频器主要特点比较Current controlled PWM inverterCurrent controlled pulse width modulationFixed-frequency PWM controlBlock diagram of a three-phase current-controlled PWM inverter feeding an ac motor 要求要求(1)1.懂得三相电压型
8、逆变器的工作原理懂得三相电压型逆变器的工作原理,能画出六能画出六阶梯工况时的波形阶梯工况时的波形;2.了解电压型逆变器多重连接的意义了解电压型逆变器多重连接的意义,及其连接及其连接方法方法;3.懂得采用脉宽调制懂得采用脉宽调制(PWM)的意义及采用脉宽调的意义及采用脉宽调制所带来的好处和坏处制所带来的好处和坏处;4.能说明正弦脉宽调制的原理能说明正弦脉宽调制的原理,及采用正弦脉宽及采用正弦脉宽调制后谐波分布的大致规律调制后谐波分布的大致规律;5.能说明对交流电机进行变频调速时能说明对交流电机进行变频调速时,脉宽调制脉宽调制的载波频率是如何随基波频率而调节的的载波频率是如何随基波频率而调节的;6
9、.明白规则采样脉宽调制的原理及其应用场合明白规则采样脉宽调制的原理及其应用场合;要求要求(2)7.了解特定谐波消除法的原理了解特定谐波消除法的原理;8.懂得能耗制动的原理及电压型逆变器的能懂得能耗制动的原理及电压型逆变器的能耗制动能力耗制动能力;9.能说明若想使制动能量回馈电网应使用怎能说明若想使制动能量回馈电网应使用怎样的电路结构样的电路结构;10.了解顺序换相式电流型逆变器的电路结构、了解顺序换相式电流型逆变器的电路结构、工作原理和动作波形工作原理和动作波形;11.能说明能说明PWM电流型逆变器的电路结构和工电流型逆变器的电路结构和工作原理作原理;12.了解电压型逆变器和电流型逆变器的特点了解电压型逆变器和电流型逆变器的特点;13.能说明电流控制型能说明电流控制型PWM逆变器的电路结构逆变器的电路结构和工作原理和工作原理;